How to animate a character throwing their hat on the ground?
Here I explain how to use Child Of constraint to make your character pick and hold his hat.

Also, give your hat Physics > Rigid Body > Type: Active. Give the ground Physics > Rigid Body > Type: Passive. At frame 0, enable the Rigid Body > Animated option of the hat and create a keyframe. The frame before he releases the hat, create a second keyframe. The moment he releases the hat deactivate Animated and create a third keyframe, the hat should fall.